魚類から導出される心電図を利用して,強制遊泳後に疲弊したコイの生体負担度を心拍数および連続的に 計測した心拍間隔の時系列解析から求められる指標ARAVによって定量的に表すことを試みた。ここで新た に導いたARAVは,心拍変動時系列を表す自己相関モデルの白色雑音部分の分散および自己相関部分の分散 との比によって相対的な心拍変動の大きさを表すものである。一般に安静状態の魚類の心拍間隔は均一では なく,むしろランダムに間隔の長さが変動しているため,このような状態ではARAVは十分大きな値をとる しかし,極度の疲労状態に陥った魚では心拍間隔がほぼ均一となるため, ARAVが極めて小さくなる。コイ を回流水槽中で1-3BL/s, 1-3h強制遊泳させ,遊泳前および遊泳終了3h後までの回復過程における心電 図を記録した。その結果,比較的低速(1BL/s)遊泳であっても,長時間(3h)遊泳するとARAVの値が小さ くなり,またその回復も遅れた。比較的高速(3BL/s)で短時間(1h)遊泳の後にもこのようなARAVの継続 的な低下が見られ,個体差の大きい心拍数だけでは表すことの出来ない極度の疲労状態を, ARAVを指標と して表せる可能性が示された。

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In order to observe of fish behavior to the set net, a radio transmission system for underwater video image was constructed and tested. This system consists of a transmitting station on the sea and a receiving station on the land. The transmitting station is composed of an underwater video camera, a video transmitter, a transmitting antema, lead-acid batteries, a cellular phone and a sound sensor for remote control of power supply. The underwater video image is transmitted to the receiving station with microwave of l.2 GHz. The receiving station is composed of a receiving antenna, a video receiver, a monitor and a VCR. The maximum transmission distance of the system was measured with about 7 km on the sea. The test run of the radio transmission system for underwater video image was conducted on the set net fishing ground in Tateyama Bay, Chiba Prefecture. The underwater video camera was installed in front of a funnel net to observe the fish behavior to the final trap of the set net. The transmitting station was moored near the final trap and the receiving station was set up in the Banda Marine Laboratory of Tokyo University of Fisheries where is l.5 km away from the set net. The test run lasted for 23 days in November, 2002. A total of 60 hours of the underwater video image were recorded and the fish behavior of 18 species were observed clearly during the test run. The inshore fish such as rudderfish Kyphosus vaigiensis, filefish Stephanolepis cirrhifer and blackfish Girella punctata frequently swam in and out the final trap through the funnel net. In contrast, yellowtail Seriola quinqueradiata did not escape from the final trap except for only one fish.

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Construction of artificial habitats has recently received attention as a technique for environmental remediation. In order to collect fundamental information that is required to develop efficient artificial habitats for remediation, an artificial habitat with experimental units (including plates of various densities), was set-up on the sea floor of the shore of Awaji Island, Japan. We observed the transition in the composition and biomass of the benthic community that inhabited the artificial habitat over three years. The artificial habitat was inhabited by 85 sessile and 218 mobile species. The number of species and biomass differed among the experimental units. Initially, the number of species was large ; and the biomass per surface area of the plates increased as the density of the plates decreased. The temporal changes in the biomass of the species were classified into four pattems, namely 'initial increase', 'later increase' , 'seasonal fluctuation' and 'irregular fluctuation'. Although the composition of the benthic communities that formed on the experimental units differed in the early stage, the proportion of large and camivorous species was high and the communities were similar in every experimental unit by the end of the experiment. We concluded that the climax community was hardly affected by the density or surface area of the plates in the artificial habitat within the context of the experiment.

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著者らは水中での網地形状と荷重をコンピュータによって推定できる汎用性の高いシステムNaLA(Net shape configuration and Loading Analysis system)の実用化を目指してその開発に取り組んでいる。絹地形状と 荷重は数値計算により算定されパーソナルコンピュータ上に3次元的に視覚化される。本論文ではNaLAに よって得られた推定結果を水槽実験とトロール網形状推定ソフトウエアDynamiTと比較し,その性能を評 価した。計算モデル内の抗力係数をレイノルズ数の関数とすることで網地の形状とそれに作用する荷重は水 槽実験の結果とよく一致することが確認された。 NaLAとDynamiTとの性能を比較したところ, NaLAでは 早い段階で平衡状態の網形状を得ることができたが, DynamiTでは網地の脚や曳航索が折れ曲がり,網形状 が不安定な状態になることが確認され不合理な結果が得られた。これらの結果からNaLAの計算モデルで得 られる推定結果は精度,汎用性や実用型の面でより適切なものであることが確認された。

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The buoy built-in GPS receiver for ORBCOMM system was developed recently. The ORBCOMM system is a kind of remote monitoring system using the communication satellite. Using this system, the drifting position of buoy is able to be monitored on real time mostly. But the system performance is not evaluated sufficiently in actual sea condition. In this paper, we explained the concept of this new satellite monitoring system, and the results of verification experiments on positioning accuracy and GPS data communication delay time conducted at sea. And, a proposal of a small single GPS receiver added to the buoy in order to improve the positionig accuracy is made and the experimental results is also discussed.

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The performance of biodegradable plastics in seawater at various locations was examined. The seawater was sampled in the pier of Tokyo University of Fisheries, the mouth of Tama river, the mouth of Edo river, the mouth of Kyuedo river, Sagami bay and the offing in Boso peninsula. In this study, we used two samples of biodegradable plastics, polycaprolactone (PCL), and poly (3-hydroxybutyrate-co-3-hydroxyvalerate) [p (3HB/V)]. The biodegradability of their films in seawater was assessed by monitoring the time-dependent changes in the biochemical oxygen demand (BOD). The films were rapidly degraded in seawater sampled in Tokyo bay and BOD-biodegradability of their films was 42 and 92% for 7 and 23days respectively. BOD-biodegradability of films in seawater sampled in other area was Iower than that sampled in Tokyo bay. The study using the scaming electron microscope showed the films decomposed by the microorganism. The PCL-degrading microorganisms were isolated from the seawater and designated R-1, R-2 and R-3. Physiological and phylogenetic characters of these microorganisms were examined. These results show that strain R-1 was identified as Pseudomonas studomons, and strains R-2 and R-3 belong to the genus Pseudomonas. Biodegradation of PCL monofilament fiber by isolated bacteria, strain R-1 was investigated. Tensile strength of PCL monofilament was rapidly reduced to 50% for 2 days.

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漁船員の労働災害は全産業の8倍と被災率が高い。人間工学的には,多くの漁業労働災害が不十分な作業 環境に関連して発生している。本研究では,漁船労働で最も災害発生率が高い底びき網漁業を対象とした。 漁労作業時の作業者の作業動作をビデオカメラで記録して,作業安全に影響する作業者の動作分析を行い, 人間工学の観点から危険要因の研究を行った。底びき網漁船の作業者の位置,動線,作業姿勢を分析した。 作業動線の分析では,網を掛けている作業者が網の上を歩くことが観測され,この作業者の動きの範囲は広 かった。網の上を歩くことは海中転落事故を引き起こす場合があり,危険な動作である。この危険を避ける ために,作業者は手すりを使用するべきである。 魚の選別,箱入れ作業では,不自然な作業姿勢が見られ, 「つらさ指数」によって評価した。 80GTトロ ール船では,作業者は直接床に魚を置いたため, 「つらさ指数」 5以上と評価された。だが, 160GTトロー ル船のように, 2層デッキでベルトコンペヤを使用するならば,前屈の作業姿勢が減り, 「つらさ指数」は 3まで減少すると考えられる。

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A earth monitoring system which consists of a zero-phase-sequence current transformer (ZCT), current relay (OCG) and three condensers was constructed in order to detect the accident point for the lower ground fault resistance on the electrical machinery, apparatus and lines. It was installed on a a.c. 100V feeder panel in the research and training vessel Umitaka maru, while measurement was carried out to evaluate the performance of the device. As a result, the following issues were clarified. 100mA in the ground fault current was measured by this device, and then the alam of a 'lower ground fault resistance' was confimed on the data-logger when the ground fault resistance was Iowered to 0.6kΩ. In this case, the decrease of 20 mA in the ground fault current was confirmed when the condenser was not comected to the feeder. However, the detection of the lower ground fault resistance while not comected to the condenser was still possible.

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A prevention apparatus of dissolved oxygen deficiency in closed basin such as pond, lake and dam is proposed, and the possibility of the practical application of this equipment is indicated. This equipment is consisted of a vertical rotating shaft, eight radiation partition plates and two parallel disks. The horizontal radiation jet is formed by rotating the disks at the near water surface and is induced the vertical circulation flow in the cIosed basin. As the result, the dissoIved oxygen deficiency at the bottom will be restrained.

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